Band-structure engineering of ZnO by anion-cation co-doping for enhanced photo-electrochemical activity

To look for efficient visible light-driven catalysts for photo-electrochemical (PEC) water-splitting, the band structure and optical absorption of monodoped, compensated, and noncompensated n-p pairs of co-doped bulk ZnO are systemically studied by using both general gradient approximation and hybrid density functional theory approaches (PBE and HSE). Calculations show that n-p co-doping cannot only enhance the stability that stems from the strong electrostatic attraction between the n- and p-type dopants, but also effectively reduce the band-gap of ZnO. More importantly, compensated (Ti+C) and noncompensated (Sc+C) and (Cr+C) co-doped ZnO may be compelling candidates for PEC water-splitting because of their narrowed band-gaps, potentially reduced electron-hole recombination centers, appropriate band-edge positions, enhanced optical absorption, and good stability.